MAX638AEPA+

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The MAX638AEPA+ is a voltage regulator recognition within the DC to DC Switching Regulators of the PMIC voltage regulators. This compact voltage regulator is designed to deliver a varying constant output current that can be adjusted with a resistor. It follows a voltage-mode control, which is achieved by the external voltage divider. Additionally, its output current is set through the values of an external current-setting resistor.

The MAX638AEPA+ has a wide range of application fields, including low-power portable applications, such as copiers, fax machines, audio systems, and other battery-powered applications where a precise voltage regulation is required. It is suitable for applications with input voltages from 4.5V to 36V. Furthermore, its nominal output can be set from as low as 3.3V up to 19V.

Moreover, the MAX638AEPA+ has integrated startup circuitry, which includes a 3V reference, a 5mA current source for the voltage reference and a low quiescent current totem-pole PNP output stage driver. When the circuit is powered on, the output impedance is at its lowest state, to ensure the desired regulation. Beyond that, overcurrent protection is offered by an internal current-limit circuit, and thermal protection is provided by its internal shutdown circuit. This makes it a safe and reliable option.

The MAX638AEPA+ regulator works on the sliding frequency pulse width modulation (PWM) control principle. This PWM control circuit helps in detecting the output voltage, with a certain accuracy and stability, by using a low quiescent current reference compared to the load current. Since its control circuitry works in open loop, it is not affected by the changing load current. The targeted constant output voltage is established by a voltage-scaling network, composed of two resistors, connected to the PWM control circuit.

The MAX638AEPA+ works on the principle of pulse frequency modulation, or PFM in short. PFM is the process by which the output of the regulator is pulsed at a fixed frequency, with the on time being varied according to the voltage difference between the output voltage and the reference. This process is advantageous because it allows the regulator to maintain a constant output voltage despite the variations in the load current.

The MAX638AEPA+ features current mode control, with a typical switching frequency of 400KHz. Its output current is adjusted by means of a resistor and the output voltage is regulated by an external DC reference, which is set with a two-resistor voltage divider. This regulator is easy to program, thanks to its user-friendly features. Plus, it is extremely accurate in terms of voltage regulation, as it is capable of delivering an accuracy of 0.25%.

In summary, the MAX638AEPA+ belongs to the range of DC-DC Switching Regulators within thePMIC voltage regulator. It has a wide range of application fields, including low-power portable applications that require precise voltage regulation. It works on the principle of sliding frequency pulse width modulation (PWM) control, featuring current mode control and a typical switching frequency of 400KHz. Additionally, its output voltage and current are adjustable, making it a safe and reliable voltage regulator that is accurate and easy to programme.

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